Andrew Lang (1844 - 1912) was a British poet, novelist, literary critic, and collector of folk and fairy tales. In this essay, he investigates the mystery of the man in the iron mask of Alexander Dumas' novel. Lang traces the progress of the romantic legend, as it blossomed after the death of the man whose mask was not of iron, but of black velvet. The legend struck root and flowered, from the moment when the poor valet, Martin ("Eustache Dauger"), was immured in the French fortress of Pignerol. After an exhausting and fascinating look at the evidence, Lang comes to the conclusion that, whatever masked captive died in the Bastille in 1703, the valet Dauger was the real source of most of the legends about the Man in the Iron Mask.